The present invention is situated in the field of aqueous pigment preparations.
In the production of preparations and dispersions of colorants, for example, disperse dyes or organic and inorganic pigments, for applications in aqueous or organic media, a large number of nonionic, anionic, and cationic surfactants is presently in use. The incorporation of pigments or their preparations into coating systems, printing inks, plastics, and other applications is sometimes accompanied by difficulties, since the fine and flocculation-stable dispersion of numerous pigments in the respective application medium is very unsatisfactory and involves a high level of dispersing effort. Consequently, the performance properties are very often inadequate. For instance, during the dispersing operation and thereafter as well, flocculation phenomena and formation of sediment may occur, which lead to changes in the viscosity of the application medium, to changes in shade and to losses in color strength, opacity, gloss, homogeneity, and brightness and also to shades which are difficult to reproduce and to an excessive tendency for paints to run in the case of the materials colored.
For improving the pigment properties a variety of derivatives of pigment molecules are known which are said to enhance the dispersibility. For example, for quinacridone pigments, additives are described which are based on the chemical bonding of isoindole-1,3-diones to this pigment class. One example of this class of compound is the 2-(phthalimido-methyl)quinacridone U.S. Pat. No. 4,478,968 describes for enhancing the dispersing properties of the quinacridone pigment.
EP-A-0 636 666 describes imide and bisimide derivatives which derive from perylene-3,4,9,10-tetracarboxylic anhydride and are made available by reaction with amines. These imides are suitable for producing pigment preparations.
None of the products described in the cited documents above, however, is capable of decisively enhancing the fluidity and the flocculation stability of pigment dispersions without having a deleterious influence on other parameters, such as color strength, gloss, shade, and dispersibility. One of the disadvantages of the products described in the abovementioned documents is that the soluble pigment derivatives, which are themselves intensely colored, can lead undesirably to bleeding in binder systems or in plastics and so to the staining of adjacent materials. Moreover, owing to the low solubility of the parent pigments, the preparation of pigment-derived compounds of this kind involves difficult conditions and a high cost. A further disadvantage is the limited application scope, which because of their intrinsic color remains restricted to pigments of the same or similar color.
The present invention was based on the object of providing pigment preparations which are suitable for producing highly fluid, flocculation-resistant, and storage-stable colorant dispersions for exterior and interior coating and are largely free from the disadvantages specified above.
The object stated is surprisingly achieved by adding below-specified nonpigmentary cyclic imides having aliphatic or olefinic carbon chains, which are virtually colorless or only very slightly colored, to organic or inorganic pigments.
The present invention provides pigment preparations comprising
a) at least one organic or inorganic pigment;
b) at least one cyclic imide of the general formula (1) 
where
R1 [lacuna] for a straight-chain, branched or cyclic aliphatic radical having 10 to 30, preferably 12 to 25, carbon atoms; for an alkenyl radical having 10 to 30, preferably 12 to 25, carbon atoms, it being possible for the radicals stated to be substituted by one or more, e.g., 2, 3, 4 or 5, substituents from the group consisting of C1-C6 alkyl, C1-C6 alkoxy, C6-C10 aryl, hydroxyl, carboxyl, and sulfo;
R2, R3, R4 and R5 are identical or different and denote hydrogen, C1-C10 alkyl, C1-C10 alkoxy, halogen, xe2x80x94OR6, xe2x80x94NR6R7, xe2x80x94COOR6, xe2x80x94CONR6R7, xe2x80x94NR6xe2x80x94COR7, SO2NR6R7, xe2x80x94SO3M, xe2x80x94NO2, xe2x80x94CN or CF3, R6 and R7 standing for H or an alkyl radical having 1 to 10 carbon atoms and M standing for one equivalent of a 1 to 3 valent cation, e.g. hydrogen or alkali metal; and
c) if desired, further customary additives.
Compounds of the formula (1) per se are known. These compounds are described in, for example, U.S. Pat. No. 4,992,204, but are not used together with organic pigments.
U.S. Pat. No. 6,039,769 describes the use of nonpigmentary cyclic imides having short alkyl radicals for perylene pigment preparations.
Preferred imides of the formula (1) are those wherein
R1 denotes decyl, dodecyl, tetradecyl, octadecyl, isotridecyl, lauryl, oleyl or stearyl.
Preferred imides of the formula (1) are also those wherein R2, R3, R4, and R5 are identical or different and denote hydrogen, methyl, ethyl, propyl, butyl, methoxy, ethoxy, amino, methylamino, dimethylamino, ethylamino, diethylamino, carboxyl, COOCH3, carboxamide, CON(CH3)2, sulfonamide, SO2N(CH3)2, sulfo, nitro, cyano or CF3.
The compounds of the formula (1) used in the pigment preparations of the invention can be prepared by known methods from the aromatic parent structures, preferably the cyclic anhydrides, by reaction with the corresponding fatty amines. The cyclic anhydrides are either commercially available or can be prepared easily by known methods from the corresponding dicarboxylic acids: for example, by heating and by treatment with strong acids or dehydrogenating reagents. Of the numerous fatty amines and the natural fatty amine mixtures, only the most important will be mentioned here, such as, for example, dodecylamine, tetradecylamine, octadecylamine, isotridecylamine, coconut fatty amine, laurylamine, oleylamine, rapeseed oil fatty amine, stearylamine or tallow fatty amine. In addition to the fatty amines, mention may also be made of resin amines, and the derivatives preparable therefrom. The water formed during the reaction may be removed distillatively with the addition where appropriate of an azeotrope former: for example, a hydrocarbon or chlorohydrocarbon.
Preferably, however, the amide formation is carried out without solvent simply by distillative removal of the water of reaction formed. Owing to the quantitative yields of amide there is no need for further purification or treatment of the product.
Examples of organic pigments in the sense of the invention are monoazo pigments, disazo pigments, disazo condensation pigments, laked azo pigments, triphenylmethane pigments, thioindigo pigments, thiazine indigo pigments, perylene pigments, perinone pigments, anthanthrone pigments, diketopyrrolopyrrole pigments, dioxazine pigments, quinacridone pigments, phthalocyanine pigments, isoindolinone pigments, isoindoline pigments, benzimidazolone pigments, naphthol pigments and quinophthalone pigments, preference being given to anthanthrone pigments, dioxazine pigments, and phthalocyanine pigments, and also acid to alkaline carbon blacks from the group of the furnace blacks or gas blacks.
Examples of suitable inorganic pigments are titanium dioxides, zinc sulfides, iron oxides, chromium oxides, ultramarine, nickel and chromium antimony titanium oxides, cobalt oxides, and bismuth vanadates.
Preferred pigment preparations contain
a) 5 to 60% by weight, especially 10 to 50% by weight, of pigment;
b) 0.1 to 15% by weight, especially 0.5 to 10% by weight, of the imide of the formula (1);
c) 0 to 50% by weight, especially 1 to 30% by weight, of further additives; and
d) 10 to 80% by weight of water, based on the total weight of the pigment preparation.
Examples of further additives are anionic, cationic or nonionic surfactants, foam-reducing agents, agents which prevent the preparation drying out, and preservatives.
Suitable surfactants include all known anionic, cationic, and nonionic surface-active compounds. Surfactants which possess one or more medium- or long-chain hydrocarbon chains have proven themselves particularly. Of the multiplicity of compounds only a selection will be listed at this point, without, however, restricting the applicability of the compounds of the invention to these examples. Examples are alkyl sulfates, alkenyl sulfates, alkylsulfonates, alkenylsulfonates, alkyl phosphates, alkyl-benzenesulfonates, such as lauryl sulfate, stearyl sulfate, dodecyl-sulfonates, octadecyl sulfates, dodecylsulfonates; condensation products of fatty acid and taurine or hydroxyethanesulfonic acid, alkoxylation products of alkylphenols, castor oil rosin esters, fatty alcohols, fatty amines, fatty acids, and fatty acid amides, especially reaction products of nonylphenol and relatively short-chain, substituted alkylphenols and also their polymeric derivatives, e.g., formaldehyde condensation products.
The use of surfactants having identical or very similar aliphatic radicals to prepare the pigment dispersions of the invention gives dispersions having particularly good and application-friendly properties.
The present invention also provides a process for producing the pigment preparations of the invention by adding the compound(s) of the formula (1) and, where appropriate, the further additives during the pigment synthesis, or during one of the customary finishing steps such as grinding, dispersing or solvent treatment or else not until during the incorporation of the pigment into the application medium. The compound of the formula (1) can be added in solid or dissolved form to the pigment, which is present as a solid or as a dispersion in water or an organic solvent.
Dispersing and grinding operations take place conventionally in accordance with the hardness of the pigment used: for example, in sawtooth stirrers (dissolvers), rotor-stator mills, turbulent high-speed mixers, ball mills, sand mills or bead mills, in kneading apparatus or on roll mills.
The liquid- to pastelike pigment preparations prepared in this way are available for any purpose for which colorant dispersions are normally employable and for which exacting requirements are imposed on flocculation and/or storage stability, changes in viscosity of the application medium, shade changes, color strength, opacity, gloss, homogeneity, and brightness. Thus they are suitable, for example, for the coloring of natural and synthetic materials. They are particularly valuable, in accordance with the invention, for the preparation of paints and/or printing inks, and also for the coloring of plastics and high molecular mass materials, but preferably for the preparation of pigment dispersions which further comprise one or more surfactants, water, customary amounts of builder substances or other customary additives or auxiliaries which are used in emulsifying and dispersing formulations, such as, for example, additives which delay the formulation drying out. Aqueous dispersions prepared on this basis are outstandingly suitable for pigmenting both hydrophilic and hydrophobic systems.
As well as the preparation of pigment dispersions the compounds of the invention can also be used, preferably in combination with surfactants, to prepare dispersions of dyes, optical brighteners, and also for formulating crop protection and pesticide compositions and additionally as emulsifying, leveling, and dyeing assistants for the dyeing of natural and synthetic fiber materials.
The pigment dispersions of the invention are suitable as colorants in electrophotographic toners and developers, such as one- or two-component powder toners (also called one- or two-component developers), magnetic toners, liquid toners, latex toners, polymerization toners, and specialty toners, for example.
Typical toner binders are addition polymerization, polyaddition and poly-condensation resins, such as styrene, styrene-acrylate, styrene-butadiene, acrylate, polyester, phenolic-epoxy resins, polysulfones, polyurethanes, individually or in combination, and also polyethylene and polypropylene, which may include further ingredients, such as charge control agents, waxes or flow assistants, or may be modified subsequently with these additives.
Furthermore, the pigment dispersions of the invention are suitable as colorants in powders and powder coating materials, especially in triboelectrically or electrokinetically sprayable powder coating materials, which are used to coat the surfaces of articles made, for example, of metal, wood, plastic, glass, ceramic, concrete, textile material, paper or rubber.
Typical powder coating resins used include epoxy resins, carboxyl- and hydroxyl-containing polyester resins, polyurethane resins, and acrylic resins, together with customary curatives. Resin combinations are also employed. For example, epoxy resins are frequently used in combination with carboxyl- and hydroxyl-containing polyester resins. Typical curative components (depending on the resin system) are, for example, acid anhydrides, imidazoles and also dicyandiamide and its derivatives, blocked isocyanates, bisacylurethanes, phenolic resins and melamine resins, triglycidyl isocyanurates, oxazolines, and dicarboxylic acids.
In addition, the pigment dispersions of the invention are suitable as colorants in inks, preferably ink-jet inks, such as those on an aqueous or nonaqueous basis, for example, in microemulsion inks, and in those inks which operate in accordance with the hot-melt process.
Ink-jet inks generally contain in total from 0.5 to 15% by weight, preferably 1.5 to 8% by weight (calculated on a dry basis), of the pigment dispersions of the invention.
Microemulsion inks are based on organic solvents, water, and, where appropriate, an additional hydrotropic substance (interface mediator). Microemulsion inks contain 0.5 to 15% by weight, preferably 1.5 to 8% by weight, of the pigment dispersions of the invention, 5 to 99% by weight of water, and 0.5 to 94.5% by weight of organic solvent and/or hydrotropic compound.
Solvent-based ink-jet inks contain preferably 0.5 to 15% by weight of the pigment dispersions of the invention, 85 to 99.5% by weight of organic solvent and/or hydrotropic compounds.
Hot-melt inks are based generally on waxes, fatty acids, fatty alcohols or sulfonamides which are solid at room temperature and become liquid on heating, the preferred melting range being situated between about 60 and about 140xc2x0 C. Hot-melt ink-jet inks consist essentially, for example, of 20 to 90% by weight of wax and 1 to 10% by weight of the pigment dispersions of the invention. Furthermore, 0 to 20% by weight of an additional polymer (as xe2x80x9cdye dissolverxe2x80x9d), 0 to 5% by weight of dispersing auxiliary, 0 to 20% by weight of viscosity modifier, 0 to 20% by weight of plasticizer, 0 to 10% by weight of tack additive, 0 to 10% by weight of transparency stabilizer (prevents, for example, crystallization of the waxes), and 0 to 2% by weight of antioxidant may be present. Typical additives and auxiliaries are described in, for example, U.S. Pat. No. 5,560,760.
Moreover, the pigment dispersions of the invention are also suitable as colorants for color filters, both for additive and for subtractive color generation, and for xe2x80x9celectronic inksxe2x80x9d.
The pigment dispersions prepared in accordance with the invention are miscible with water in any proportion as compared with conventional pigment dispersions feature an outstanding flocculation stability and storage stability in numerous aqueous emulsion paints. Where surfactants compatible with hydrophobic film-forming binder systems are used in preparing the pigment dispersions, it is also possible to prepare dispersions which are stable to flocculation in hydrophobic media. Particularly noteworthy features include the good rheological properties and also the excellent dispersibility in different application media.
The compounds of the invention therefore make it possible, preferably in combination with an appropriate surfactant, to achieve virtually the full color strength and brightness of pigments during the dispersing operation and to stabilize these qualities lastingly in the application medium. Pale and bright shades are unaffected by the minimal intrinsic coloration of the compounds.